Could President-elect Trump be the leader who finally moves the American Embassy in Israel to Jerusalem? He promised during his campaign to implement the Jerusalem Embassy Act of 1995, which calls for Jerusalem to be recognized as the capital of the State of Israel and for the Embassy to be established in that city.

Unlike predecessors who made similar promises right up to Election Day only to abandon those promises once in office, Mr. Trump has continued to stand by his word. Now the question is how best to keep that promise while the new president still enjoys the ever-shorter honeymoon period of a new administration.

If Mr. Trump tasks the State Department with building a new embassy brick by brick, the forces that convinced his predecessors to ignore the Jerusalem Embassy Act will conspire to make certain that not a single brick is ever laid. However, the President-elect has another option that would fulfill his campaign promise on his first day in office – and be his most miraculous Trump “construction” project ever.

For it turns out that America already has a beautiful, historic diplomatic mission situated in the western part of Jerusalem, a short walk from Jaffa Gate. It is on land that is clearly on Israel’s side of the Green Line. The building currently houses the political offices of the Jerusalem Consulate General and the office of the Consul General.

Our diplomatic mission in Jerusalem dates back to 1844 and the administration of President Tyler. Yet the American Consul General and his mission have no official relationship with the State of Israel. They focus virtually all of their attention on the Palestinian Arab population of East Jerusalem, Gaza, and the West Bank.

The Jerusalem Consul General is our only consul who does not present diplomatic credentials to the sovereign power in which his consulate is situated. Not only is he unaccredited to the State of Israel, but he has no official connection to the American ambassador to Israel. Instead, he reports directly to the Department of State in Washington.

The presence of the Consulate General causes no small amount of confusion and consternation among the Israelis, including many American citizens. They see the American flag flying proudly over an American Government installation in the heart of Jerusalem that is unwelcoming to Jerusalem’s Jewish citizens, even as the State Department refuses to recognize Jerusalem as Israel’s capital.

With a single Executive Order, President Trump can succeed where all of his predecessors failed, and at scant cost to the taxpayer. All he needs to do to fulfill the long-thwarted intent of Congress and implement the Jerusalem Embassy Act is to hang a “United States Embassy” sign on the existing building, give our ambassador to Israel an office there, and bring the Consul General under the ambassador’s authority.

The large embassy in Tel Aviv could continue to function, just as America maintains parallel diplomatic missions in Pretoria and Cape Town in order to be connected to South Africa’s administrative and legislative capitals. This Executive Order would make an unmistakable statement to Israel and the world that America strongly supports Israel’s right to exist as the nation state of the Jewish people with Jerusalem as its capital.

Plus, I believe we would see a surprise — a prompt and positive impact on efforts to resolve Israel’s conflict with the Palestinian Arabs. Israel once again would be confident of the support of its most important ally (confidence that was shaken during the Obama administration), and would be more willing to accommodate the other side.

Palestinian leaders finally would be disabused of the notion that the Jewish presence in Jerusalem (and all of Israel) is only temporary. They would recognize the need to negotiate a final resolution of the dispute with their permanent neighbor. It’s not as if the opposite strategy has worked.

Building a full-fledged embassy building anywhere in the world is an expensive and time consuming process. Such a project would have no chance of completion during President Trump’s first term in office. Implementing the Jerusalem Embassy Act without lifting a shovel would be a uniquely “Trumpian” solution to a long-festering problem.

Designating the Jerusalem Consulate General as the American Embassy to Israel and relocating our ambassador, thereby recognizing Jerusalem as Israel’s rightful capital, is a strategy made to order for President Trump. He can keep his campaign pledge, honor the intent of Congress, and right an historical wrong, all without charging the taxpayer for a single brick.

Mr. Cohen’s 24 years of service with the American State Department included two tours in Israel, where he is now a fellow at Bar-Ilan University’s Center for International Communication.